1. Field of the Invention
This invention relates to an ignition timing control system for internal combustion engines, and more particularly to a system for deciding the amount of ignition timing retard adjustment in an internal combustion engine.
2. Description of the Prior Art
In conventional internal combustion engine ignition timing control a basic ignition timing is calculated from the engine speed, load and the like, an adjustment amount is calculated based on the engine coolant temperature, the intake air temperature, the presence/absence of knock etc., and the adjustment amount is added to the basic ignition timing to obtain the final ignition point. For example, Japanese Patent Publication No. 2(1990)-36787teaches a system in which occurrence of knock is prevented by retarding the ignition timing when the engine coolant temperature is higher than a prescribed value. On the other hand, as can be seen in Japanese Laid-open Patent Publication No. 2(1990)-64263, for example, systems have recently been proposed for enhancing vehicle performance by retarding the ignition timing so as to reduce engine output torque.
However, since the prior art internal combustion engine ignition timing control separately calculates the retard adjustment amount for avoiding knock and the retard adjustment amount for reducing engine output torque, the amount of retard adjustment becomes excessive and the performance of the vehicle is degraded when an engine operating condition producing knock and an engine operating condition requiring engine output reduction are present at the same time.